Uniformly labeled proteins and amino acids promise to become very powerful tools for the study of protein metabolism in humans and other animals. This project will test the feasibility of economically producing uniformly labeled ribulose-1,5-bisphosphate carboxylase/oxygenase, a vegetable protein, using the isotopes H-2, C-13 and N-15. Two approaches will be used in this project to determine which approach will be most cost effective. The first approach is by fermentation of a heterotrophic clone containing the genes for this protein. The second approach will be by photosynthetic incorporation of isotope using cyanobacterial clones. The end result of this project, if successful, will be an economical production scheme for this labeled protein.